From DVLA website:

"In order to retain the original registration mark:

*

Cars and Car-Derived Vans must use:

The original unmodified chassis or unaltered bodyshell (i.e. body and chassis as one unit - monocoque); or

A new chassis or monocoque bodyshell of the same specification as the original supported by evidence from the dealer/manufacturer (e.g. receipt)

And two other major components from the original vehicle - see list below

* Suspension (front & back)

* Axles (both)

* Transmission

* Steering Assembly

* Engine

If a second-hand chassis/monocoque bodyshell is used, the vehicle must pass a ESVA/SVA test after which a "Q" prefix registration number will be allocated."


The only way to get round this legitimately it seems is to make some body shell changes and register it as a kit car.